Cleaning up after a Camel

Now that my port of CamelForth-80 to the Sega SG-1000 is sort of working, it’s time to get it working better. There’s a lot of undone odds and ends and little bugs that I need to take care of before I can try running it on real hardware, so this week’s (abbreviated) effort was mostly along those lines. VDP Delay The Sega SG-1000 is designed around the Texas Instruments TMS9918A video display processor. A lot of great machines use chips in this family, including the ColecoVision, the original series of MSX, the VTech CreatiVision, the BBC Bridge Companion, and the Sord M5. In fact, it’s pretty common to see posts about the TMS99xx around these parts. Originally, this part was designed for the TI99/4A. Being such a complex part, it does have its little foibles, and one of them is that it takes the chip awhile to “start up” before it will respond properly to commands. We saw this problem back when I was building the Sega SG-1000 RAM test cartridge, where we found that if I started doing…